1. Field of the Invention
The present invention relates to a refrigerant flow-amount controlling device and an ejector refrigerant cycle system having an ejector. For example, the refrigerant flow-amount controlling device is suitably used for an ejector refrigerant cycle system.
2. Description of the Related Art
JP-A-2005-308380 (US 2005/0268644 A1) proposes an ejector refrigerant cycle system in which a branch portion is provided at an upstream side of a nozzle of an ejector. In this cycle system, one refrigerant stream from the branch portion flows into the nozzle portion of the ejector, and the other refrigerant stream from the branch portion flows into a refrigerant suction port of the ejector.
Furthermore, a first evaporator is located for evaporating refrigerant flowing out of the ejector, and a throttle mechanism and a second evaporator are located between the branch portion and the refrigerant suction portion. Therefore, refrigerant decompressed in the throttle mechanism flows into the second evaporator and is drawn into the refrigerant suction port of the ejector.
In the ejector refrigerant cycle system, a flow amount Gn of refrigerant passing through the branch portion is the total of a flow amount Gnoz of refrigerant flowing into the nozzle portion from the branch portion and a flow amount Ge of refrigerant flowing into the refrigerant suction port from the branch portion through the second evaporator (i.e., Gn=Gnoz+Ge). Accordingly, when the flow amount Gnoz is increased, the flow amount Ge is decreased, thereby decreasing the cooling capacity of the second evaporator. In contrast, when the flow amount Ge is increased, the flow amount Gnoz is decreased, thereby reducing a refrigerant suction capacity and a pressure increasing amount in the ejector.
Accordingly, it is difficult to suitably divide the flow amount Gn of refrigerant at the branch portion into the flow amount Gnoz of refrigerant flowing into the nozzle portion and the flow amount Ge of refrigerant flowing into the refrigerant suction port of the ejector while the cycle system has a high efficiency in the whole cycle. That is, a flow ratio between the flow amount Ge and the flow amount Gnoz is difficult to be suitably controlled in accordance with cooling load in the cycle system.